The tool aims to show how efficient a server is at different types of work

SPEC, the standards body for performance benchmarks, has developed a tool-kit to help more accurately measure the energy efficiency of servers.

The Server Efficiency Rating Tool, released in beta on Thursday, will be used for the U.S. Environmental Protection Agency's Energy Star for Servers program, which is supposed to help companies identify the most efficient servers when making purchase decisions.

It's become an important topic as companies struggle with rising energy costs in their data centers. But it's been difficult to measure the efficiency of new equipment, with vendors making all kinds of competing claims.

The first Energy Star for Servers program, introduced two years ago, aimed to address that, but some see it as a good first effort that didn't go far enough. It looks at the efficiency of server power supplies and power consumption at idle, but it doesn't measure efficiency running actual workloads.

That's a more difficult challenge that SPEC is trying to address. It identified various server functions, such as XML mapping, encryption, and FFT (fast Fourier transformation), and SERT measures the power consumption and performance of servers while performing those functions at different load levels.

The SERT results will be used with version 2.0 of the Energy Star for Servers program, which is due to go into effect in early 2013, said Klaus-Dieter Lange, chair of the SPECpower committee, which is developing SERT.

Server vendors will use the toolkit to measure the efficiency of their servers, then submit the results to the EPA for certification. The EPA is still deciding how the results will be presented. It might provide an aggregate rating based on all the different workload types, or it might list each result individually, so a customer buying a server for a security application, for example, could choose one that performs encryption efficiently. It could also do both.

It remains to be seen how accurately the ratings will reflect the efficiency of a server running real-world applications. And server makers will have to buy into the idea, though most are represented on the committee developing the test kit.

It's been tricky getting them to agree on how efficiency should be measured. The goal is to ensure a level playing field and not favor any one vendor.

"Getting everybody on the same page is of course very challenging," said Lange. "My goal is not to make everybody happy, but to make everybody equally unhappy. No one should have an advantage."

SERT is being developed with input from the EPA, but SPEC is also talking to international bodies about its use, Lange said.

"If widely adopted, [SERT] should reduce testing burdens on the server industry and enable more meaningful and consistent comparisons among products sold in different regions of the world," said Robert Meyers, the EPA's data center product lead, in a statement.

The Energy Star for Servers program covers two-and four-socket x86 rack and tower servers. The next version will add x86 blade servers, Lange said. SERT is "hardware-neutral," he said, so it could be used to measure other types of system as well, such as RISC servers.